In many parts of rural America, it is common for roads carrying motor vehicular traffic to cross railroad tracks without gates, warning lights, or signalling means being provided to warn the motorist of oncoming trains. In such circumstances at these unguarded crossings, it is incumbent upon the motorist to approach the crossing carefully, to look and to listen for approaching trains, and to proceed only with assured clearance before any approaching trains. This "self-help" philosophy works satisfactorily when careful, alert motorists approach the unguarded crossing. However, this system contains many traps for the unwary, careless, distracted or impaired motorist, or motorists approaching the railroad crossing under conditions of reduced visibility such as fog, falling snow, etc.
Frequent users of such an unguarded railroad crossing easily become careless about attentively looking for approaching trains. Seldom-used rail lines easily lull the motorist into false security about the improbability of an approaching train. The motorist may easily forget, become careless, rushed or otherwise approach the rail crossing without employing prudent safety measures. When, as typically happens, the careless motorist nevertheless navigates the railroad crossing without incident, the sense of security increases. Such inattentiveness prepares the motorist for disaster when a train approaches.
The infrequent user of a particular unguarded railroad crossing is likewise subject to certain dangers. Lacking descending gates, bells, warning lights or other conspicuous means of drawing the motorists attention to the crossing, the inattentive motorist not familiar with the particular road may not notice the approaching rail crossing until it is too late to take prudent safety measures with consideration of the speed of his or her vehicle. During periods of darkness, inclement weather, or any condition of reduced visibility, it becomes that much more difficult for the motorist to observe and then identify the unexpected railroad crossing. The motorist not expecting a rail crossing may be slow to detect and identify the crossing, slow to react in safely slowing the vehicle, and slow to look and listen for approaching trains. Once again, the infrequency of use of the particular railroad by trains almost always rescues the inattentive motorist from the consequences of his or her negligence. However, the results are serious indeed when the unmindful motorist encounters the infrequent approaching train.
Railroad corporations have employed a variety of safety measures to increase the safety of crossings. Descending gates seem to be the preferred means of maximizing motorist safety from the dangers of approaching trains. Along with descending gates, warning bells and flashing lights are also employed to arouse the possibly lackadaisical motorist with the warning of an approaching train. At rail crossings of the highest traffic volume, descending gates, flashing lights and bells all are typically employed for maximum warning to the motorist of an approaching train. However, there are many other rail crossing locations at which only flashing lights and bells are used, without descending gates.
The use of flashing lights, bells and descending gates have several safety effects. The descending gates make it physically much more difficult for the motorist to cross the railroad track. The gate directly in the path of the motorist makes it all but impossible for the motorist to fail to receive the information that a train is approaching and adjustment of driving is required. In addition, the descending gates, lights and bells are customarily activated only when a train is approaching. Therefore, the motorist learns to take no special safety precautions at such rail crossings unless and until the motorist is warned by activation of the gates, lights and/or bells. When such a motorist approaches an unguarded rural crossing, the mental processes of the motorist must be adjusted in several important ways. The motorist must first detect the rail crossing itself, typically by noticing an unlighted sign (typically, but not always, containing only reflectors). The motorist must then realize that this particular crossing carries no train-activated warning system. Therefore, contrary to his learned behavior from guarded crossings, the motorist must proceed only after conducting a cautious investigation for himself for approaching trains, even in the absence of special warning lights, bells or gates. It is not difficult to understand how an inattentive, lackadaisical or negligent motorist may not make these mental adjustments quickly enough to guarantee safety upon the sudden encounter of an unguarded rail crossing.
It would be prohibitively expensive for railroads to provide the customary train-activated gates, bells or warning lights at all such rural, presently unguarded, crossings. The expense typically involves the acquisition and installation of the safety devices as well as the inspection of the devices to insure proper functioning. Maintenance may be especially time-consuming and expensive due to the far-flung and numerous rural crossings added to the inspector's duties. However, maintenance must not be diminished since a malfunctioning train-activated warning device is especially dangerous for the motorist. Such motorist may have come to rely on the absence of warning as a clear indication of the absence of an approaching train. The absence of warning in spite of the presence of an approaching train (due to a malfunctioning warning device) could seriously increase the liability of the railroad for subsequent train-vehicle collisions.
In addition to the expense of acquisition, installation, and maintenance of many rural railroad crossing warning systems, the expense is further increased by the absence of convenient electrical power at many such locations. Battery operated warning systems exacerbate the problems of upkeep and maintenance by requiring frequent inspections and replacements or recharges of the battery.
However, formerly rural, rarely used, crossings may quickly become subject to heavy flows of motor vehicle traffic as living patterns, and the expansion of metropolitan areas, quickly spread population into rural regions. It has frequently been the case that railroads have been unable to keep up with the expansion of urban areas in their installation and maintenance of crossing safety devices appropriate for greatly increased traffic volume.
For these reasons, there is an apparent need for a self-contained, self-powered, train-activated railroad crossing warning device. The present invention provides such a device with battery power, rechargeable from available incident solar radiation, and activated by a digitally-encoded radio signal from the approaching train. The device of the present invention may also be used in conjunction with power delivered to the crossing location by conventional electrical lines, and need not rely exclusively on battery power. However, even with convenient access to electrical power, the device of the present invention offers several advantages in performance and convenience, as described in detail below. Although the capability of self-contained operation remote from sources of electrical power is one important advantage of the present invention, it is not the only such advantage.
The present invention also provides self-diagnosis for various conditions of malfunction, such as low battery, malfunctioning or burned out warning lights, bells, etc. The maintenance expense is considerably reduced by the practice of the present invention by the provision of communication from the crossing warning device back to the approaching locomotive. The locomotive thus collects from each crossing it encounters, suitably encoded information concerning location and the condition of the warning device and the need for maintenance. This information may be collected frequently by railroad maintenance personnel from the locomotive to provide for specific maintenance at much reduced costs, by permitting maintenance workers to skip visits to crossing signals reporting that all is well. Use of the locomotive as the receiver for such self-diagnostic information from the crossing warning device permits a low power, short range transmitter to be used by the crossing device itself. Thus, interference from numerous devices transmitting to a central maintenance facility is avoided, and power consumption is kept small.
The present invention makes use of the "Global Positioning System" (hereinafter, "GPS") to allow the locomotive to determine its location to an accuracy of typically several yards. GPS is a satellite signalling system allowing any properly equipped GPS receiver on earth to determine its location rapidly and reliably. The present invention uses GPS to locate the train for purposes of controlling nearby crossing signals, and only those designated crossing signals. The length of the train would typically be entered into the locomotive's on-board computer system at the start of each run. This allows the GPS data concerning the location of the locomotive to be easily translated into information concerning the location of both the front and rear of the train (accurate typically to within several yards). The GPS data is also used in the present invention to signal a warning to all trains in the vicinity should the particular train become disabled and obstruct the tracks. Transmission of such emergency "May Day" signals alerts all nearby trains to take appropriate collision-avoidance procedures, and provides all approaching trains with the locations of the front and rear of the disabled train.
GPS positional information from the locomotive is easily used to calculate, in an approximate manner, the locomotive's speed and direction. Consecutive locations of the locomotive may be subtracted to approximate the distance and direction of the locomotive's travel. Dividing the distance travelled by the time required to traverse such distance gives an approximation of the locomotive's speed. However, such information will not be highly precise due to two primary sources of error: 1) the inherent errors in the GPS location of the locomotive will increase in relative effect as differences between two such locations (typically, not too far apart) are employed to compute distance and speed; and, 2) curvature of the locomotive's path between two consecutive GPS readings will not typically be known, leading to errors in the computation of the locomotive's speed, distance travelled, and direction of travel. (It is possible that data for each rail line could be stored in the appropriate computer, including track curvature at each GPS location along each rail route. This route information could then be used to estimate, and reduce, the curvature errors noted above. However, it is presently believed that the increased complexity of such collection, storage and utilization of detailed route data will typically not be worth the extra efforts required. This may not always be the case, and the present invention permits such direct generalization.)
Devices have been developed to provide for warning motor vehicles of the approach of emergency vehicles, and to adjust intersection lights accordingly (U.S. Pat. Nos. 3,784,970; 3,997,868; 4,704,610; 4,775,865). However, these devices do not address the particular problems associated with remote, rural railroad crossings; typically, the need for self-diagnostic information related to the condition of the device, or the inclusion of digital encoding for selective activation and interrogation of each warning device. In addition, such devices typically send indiscriminate signals to all intersections and vehicles within range based merely on the strength of signal. Unlike the present invention, such devices do not provide for the signalling vehicle to determine its location and send coded signals for activating specific devices. Such features, and several other novel features as described in detail below, are provided by the device of the present invention.